DESCRIPTION (Verbatim from Applicant's Abstract): Renal vascular disease is an important cause of hypertension and renal ischemia. Of the 60 million Americans with hypertension, 1 - 5 percent have a renal vascular etiology. In addition, an estimated 15 percent of all patients with severe renal failure have renal artery stenosis (RAS) and ischemic nephropathy. The long-term objective of this project is to improve the prognosis of patients with vascular diseases of the kidney, such as renovascular hypertension and ischemic nephropathy. While several techniques that evaluate either the anatomy or functional significance of renal artery disease are available, no single method is capable of providing unambiguous information regarding both the anatomic and functional significance of RAS simultaneously. Magnetic resonance imaging (MRI) evaluation of RAS has several potential advantages relative to existing techniques. The method proposed in this project provides a rapid and minimally invasive technique for evaluating the renal function in each kidney that is currently not available from any other techniques. We propose to continue developing an MRI method for determining glomerular filtration rate, an important measurement of renal function, in a series of in vitro and in vivo experiments. First, we propose to develop and validate a novel method for determining renal extraction fraction (EF) using a fast inversion-recovery MRI technique. Secondly, we will develop and validate a method for measuring renal blood flow (RBF) in vivo that is capable of higher spatial and temporal resolution than existing techniques. Finally, we will measure changes in RBF, EF, and single kidney glomerular filtration rate (skGFR) following angiotensin converting enzyme (ACE) inhibition in swine models of renovascular hypertension and ischemic nephropathy. If successful, the method developed in this study will lead to a new understanding of the physiologic effects of RAS, and would help guide experiments in humans.